Carbon electrodes having stabilized binders derived from the entire organic fraction of bituminous coal

Abstract

Carbon electrodes, either prebaked or Soderberg, made with coal or petroleum coke aggregate and an industrially stable binder that is derived from the entire organic fraction of bituminous coal and is suitable for manufacturing carbon electrodes according to existing industrial practice in the electrometallurgical industries. The binder is prepared by digesting the coal with a solvent to make a purified pitch, and industrial stability is imparted by fluxing the purified pitch at about 200°-300° C.

What is claimed is: 
     
       1. A carbon electrode for use in electrometallurgical manufacturing which consists essentially of a coke aggregate and a stabilized binder having a softening point between about 100° and 150° C that is prepared by heat-treating a concentrated solution of all of the low-volatile organic materials in a bituminous coal, said concentrated solution containing 16-30% of an aromatic liquid hydrocarbon creosote-oil type solvent for said organic materials. 
     
     
       2. The carbon electrode of claim 1 wherein said heat-treating comprises fluxing said concentrated solution in air at 160°-310° C so that said binder is oxidatively and thermally stabilized and is suitable for making metallurgical electrodes according to industrial practice. 
     
     
       3. The carbon electrode of claim 2 wherein said binder is prepared by solvent refining said bituminous coal by the steps of digesting said coal with said solvent to form a fluid solution and by removing the insoluble inorganic material from said fluid solution to form a purified solution. 
     
     
       4. The carbon electrode of claim 3 wherein said purified solution is concentrated by removing at least a portion of said solvent from said purified solution to form a solvent refined pitch, as said concentrated solution, whereby high-volatile organic materials are removed from said solvent. 
     
     
       5. The carbon electrodes of claim 4 wherein said stabilized binder undergoes no significant degree of molecular rearrangement below about 450° C. 
     
     
       6. The carbon electrodes of claim 4 wherein said stabilized binder undergoes no more than about a 5° increase in the softening point thereof during storage at about 170° C. while exposed to air. 
     
     
       7. In the industrial manufacture of carbon electrodes from a coke aggregate and a binder to form a paste which is baked to about 1,200° C in approximately 48 hours to form said electrodes, the improvement comprising the preparation of said binder from substantially all of the low-volatile organic materials in a bituminous coal by solvent refining said coal in the presence of hydrogen to form a pitch containing 16-30 percent of an aromatic liquid hydrocarbon creosote-oil type solvent and by thermally and oxidatively stabilizing said pitch by fluxing said pitch in air at 160°-310° C. 
     
     
       8. A carbon electrode for use in electrometallurgical manufacturing which consists essentially of a carbonaceous aggregate and a stabilized binder which is derived from the entire low-volatile organic fraction of a bituminous coal without thermal or catalytic cracking thereof, which undergoes no more than about a 5° increase in the softening point thereof during storage at about 170° C while exposed to air, and which is oxidatively and thermally stabilized so that it is suitable for mixing with said carbonaceous aggregate for making metallurgical-grade carbon electrodes, said stabilized binder being prepared by: A. admixing a solvent, selected from the group consisting of anthracene oil and cathode pitch having a softening point of about 60° C, with 70-85% of a solvent refined coal to form a binder mixture; and   B. selectively heat treating said binder mixture without molecular rearrangement thereof to form said stabilized binder.   
     
     
       9. The carbon electrode of claim 8, wherein said heat treating comprises fluxing said binder mixture in air at a temperature of 180°-300° C. 
     
     
       10. The carbon electrode of claim 9 wherein said solvent refined coal is mixed with 17-23% of said anthracene oil prior to said fluxing.